Multiple motor hydraulic drive system



- ay 5, 1970 J. M. CRAWFORD 3,509,721

MULTIPLE MOTOR HYDRAULIC DRIVE SYSTEM Filed March 28, 1969 2Sheets-Sheet 1 ENG/NE INVENTOR. (/OHA/ A//Z 6X24 WFOE/J y 1970 J. M.CRAWFORD 3,509,721

MULTIPLE MOTOR HYDRAULIC DRIVE SYSTEM Filed March 28, 1969 2Sheets-Sheet a ILEZ 45 44 35 MJA 25 24 /5 MM LEM-57E I?) I2 ENG/NE-ENG/NE- 2 ave/[v5- 5 I 22 22 22 AUX/L/AEY a AUX/U42) E AUX/L/AEYEQU/PME/W' EOU/PMEA/T EOU/PMEA/T 2a 2a 26 I 34 c. 1 c. u g PUMP PUMP lli42 I 42 a lib I111 IN @a Ill 65 slams INVENTOR. (/OH/V A/f. CeAm F-o/e/af 1 E4 g h United States Patent O 3,509,721 MULTIPLE MOTOR HYDRAULICDRIVE SYSTEM John M. Crawford, 121 Whitworth, Ponca City, Okla. 74601Continuation-impart of application Ser. No. 748,139,

May 27, 1968, which is a continuation-in-part of application Ser. No.540,766, Apr. 6, 1966. This application Mar. 28, 1969, Ser. No. 819,509

Int. Cl. F16d 31/06 US. Cl. 60-53 Claims ABSTRACT OF THE DISCLOSURE Asystem for driving a plurality of hydraulic motors particularly usefulon a vehicle or ship having equipment thereon required to be driven byhydraulic pressure. A prime mover drives a primary pump which may supplyfluid to both the drive system and the auxiliary equipment. In the drivesystem, the output of the primary pump is directed in parallel to aplurality of constant volume pumps having their rotors mounted on acommon shaft. Each constant volume pump has its discharge connected to ahydraulic motor to be driven, and a four-way, opencenter valve controlsthe flow of fluid from each constant volume pump to its respectivemotor, such that all motors may be operated in synchronism or each motormay be individually operated at any desired speed and in eitherdirection. Braking of the hydraulic motors is obtained by directing thedischarge from all the motors through a single control valve which maybe used to maintain a back pressure on the motors.

CROSS REFERENCES TO RELATED APPLICATION This is a continuation-in-partof applicants co-pending application entitled, Hydraulic Drive System,No. 748,139, filed May 27, 1968, which in turn is a continuation-in-partof applicants application of the same title, Ser. No. 540,766, filedApr. 6, 1966, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to improvements in hydraulic drive systems employing a pluralityof drive motors.

Description of the prior art Many vehicles and ships employhydraulically driven auxiliary equipment requiring operation at varioustimes, both when the drive system of the vehicle or ship is in operationand when such drive system is not in operation. For example, manyvehicles and ships are employed in seismic exploration utilizing ahydraulically driven vibrator. Further, such hydraulically drivenvibrators require a prime mover and pump being operated at a relativelyconstant speed for proper operation of the vibrator. Prior to myinventions, separate prime movers were required for the vibrators andthe drive systems of the vehicles or ships, resulting in excessive firstand operating costs. Further, the mechanical type drive system employedon vehicles used in seismic exploration place severe limitations on theuse of the vehicles on rough terrain, and the use of a mechanical drivesystem in a ship requires the propeller shaft to be extended through thehull of the ship, resulting in serious sealing and vibrational problems.

SUMMARY OF THE INVENTION The present drive system is particularly usefulfor driving the wheels of a vehicle having hydraulically operatedequipment, such as a seismic vibrator, thereon, and

3,509,721 Patented May 5, 1970 for driving the propellers of a shiphaving hydraulically operated auxiliary equipment thereon, but may beused in any system wherein two or more hydraulic drive motors may bedesirably utilized.

In one aspect, the present invention contemplates a system for driving aplurality of hydraulic motors comprising a primary pump having arelatively constant pressure output and being driven by a prime mover. Aplurality of constant volume pumps equal to the number of hydraulicmotors to be driven have their rotors connected to a common shaft andhave their inlets connected in parallel to the output of the primarypump. A four-way, open-center valve is provided for each constant volumepump and associated hydraulic motor, having one port connected to theoutlet of the associated constant volume pump, a second port connectedto the forward port of the associated motor, a third port connected tothe reverse port of the associated motor, and a fourth port connected tothe supply of fluid for the primary pump. A control or operating leveris connected to each of the fourway, open-center valves to selectivelydirect (a) all of the fluid discharged from the associated constantvolume pump to either port of the hydraulic motor; (b) a variableportion of the fluid discharged from the associated constant volume pumpto either port of the associated motor while directing the remainingportion of the fluid back to the fluid supply, and alternately, (c) allof the fluid discharged from the associated constant volume pump back tothe fluid supply, and all of the fluid in the hydraulic motor circulatesso that the motor may free wheel, such that both the speed and directionof rotation of each motor may be individually controlled.

An object of the invention is to provide a hydraulic drive system fordriving a plurality of hydraulic motors wherein the hydraulic motors maybe individually controlled as to speed and direction.

Another object of the invention is to provide a hydraulic drive systemfor driving a plurality of motors wherein the motive fluid pressure willbe automatically directed to the motor requiring the most power.

A further object of this invention is to provide a hydraulic drivesystem for a plurality of hydraulic motors wherein cavitation of themotors will be prevented when it is desired to slow down the systembeing driven by the hydraulic motors.

Another object of this invention is to provide a hydraulic drive systemfor a vehicle having hydraulically driven auxiliary equipment thereon,wherein the same prime mover may be used for both the drive system andthe auxiliary equipment.

Another object of the invention is to provide a drive system for avehicle wherein the vehicle will have a maximum of maneuverability andmay be operated on a great variety of different terrains.

A still further object of the invention is to provide a hydraulic drivesystem for a ship wherein the propellers of the ship may be driven bythe same prime mover as is employed for driving hydraulically operatedauxiliary equipment associated with the ship.

Another object of the invention is to provide a propulsion ystem for aship in which the propeller rotation may be quickly changed or reversedwithout changing speed of the prime mover.

Another object of the invention is to economize the construction andoperation of vehicles and ships having hydraulically operated auxiliaryequipment thereon.

Another object of the invention is to provide a 'hydraulic drive systemwhich is highly adaptable, simple in construction, and which will have along service life.

Other objects and advantages of the invention will be evident from thefollowing detailed description when read in conjunction with theaccompanying drawing which illustrates the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic illustration of ahydraulic drive system constructed in accordance with this invention.

FIG. 2 is a schematic illustration of a typical four-way, open-centervalve employed in the system of this invention.

FIG. 3 is a schematic illustration of a modification of the basic drivesystem with respect to the arrangement and plumbing of the four-way,open-center valves.

FIG. 4 is a schematic illustration of another modification which may beemployed in the basic system of this invention.

FIG. 5 is a schematic illustration of the drive system of this inventionas may be employed in ships.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings indetail, and particularly FIG. 1, reference character generallydesignates a drive system constructed in accordance with this invention.The system 10 employs a prime mover 12 of any desired type, such as adiesel engine, driving a primary pump 14. The pump 14 is a relativelyconstant pressure pump, such as a multiple piston, variable stroke pump.The fluid supply for the pump 14 is indicated on the drawing by the wordsump and will normally be simply a storage tank.

The discharge port 16 of the pump 14 is connected by a conduit 18 to theinlet port 20 of a first control valve 22 designated V in the drawing.The control valve 22 is preferably a four-way valve, and may beelectrically, hydraulically or manually controlled. One of the ports 24of the valve 22 is connected to the sump for bypassing or circulation ofthe output of the pump 14, and another port 26 of the valve 22 isconnected to hydraulically operated auxiliary equipment (not shown),such as a seismic vibrator, in the event the system 10 is employedinconjunction with such auxiliary equipment. The remaining port 28 ofthe control valve 22 is connected in parallel to the inlet ports 30 of aplurality of constant volume pumps 32.

The pumps 32 may be of any suitable type of construction, such as a vanetype pump, where the pumps will operate as motors in response to apressure differential applied across the rotors thereof, as well asfunctioning as pumps when the rotors are turned. The rotors of all ofthe pumps 32 are mounted on a common shaft 34 for the automatic transferof power between the various rotors, as will be referred to in detailbelow. It should also be noted that although the pumps 32 areillustrated in the drawing as being separate pumps, it will beunderstood by those skilled in the art that the pumps 32 could all becombined in a common housing, as is found in a multiple pump chamber,vane type pump.

A throttle valve 36 is interposed in the common connection of thecontrol valve 22 to the inlet ports 30 of the pumps 32 to control thetotal amount of fluid being directed to the pumps 32 from the primarypump 14. The throttle valve 36 will thus control the speed of rotationof the rotors of the pumps 32 to control the overall speed of operationof the drive system 10, as will be further described. The throttle valve36 is designated V, in the drawing and may be of any suitableconstruction, but is preferably manually operated.

The discharge port 38 of each constant volume pump 32 is connected to afirst port 40 of what is known as a four-way, open-center valve 42. Thevalve member (not shown) of each valve 42 is ported in such a mannerthat all of the fluid directed into the port 40 of the valve may bedirected through any one of the remaining three ports 44, 46 or 48; whenfluid is directed from port 40 to port 46, ports 44 and 48 are incommunication; a portion of the fluid entering the port 40 may bedirected through 4 either of the ports 44 or 48 while the balance of thefluid is directed out of the port 46; and while fluid is being directedfrom the port 40 through either of the ports 44 or 48, fluid may be alsodirected to the port 46 from the port 44 or 48 not connected with theport 40.

The rotor of each valve 42 is controlled by an operating lever 51, asschematically illustrated in FIG. 2, to control the flow of fluidbetween the various ports of the valve. In the full line position of thelever 51 marked F, the rotor of the valve is in such a position that allof the fluid directed into the port 40 (FIG. 1) is directed out of theport 44, while the fluid at the port 48 is directed out of the port 46.In the dashed line position marked N in FIG. 2, all of the fluid presentat port 40 of the valve is discharged through the port 46, while theports 44 and 48 are in communication with one another. In the dashedline position marked R in FIG. 2, all of the fluid present at port 40 isdischarged through port 48 and the fluid present at 44 is directed outport 46. The intermediate positions of the lever 51 between thepositions F and N, as well as between the positions R and N, control thevariable flows of fluid between the port 40 and the ports 44 or 48 whilefluid is also being directed from the other port 44 or 48 to the port46.

The port 44 of each valve 42 is connected to the A or forward port of ahydraulic motor 50, and the port 48 of each valve 42 is connected to theB of reverse port of the respective hydraulic motor 50. As illustratedin FIG. 1, four of the motors 50, designated M M M and M, are employedwhich may be, for example, for the purpose of driving the four wheels 52of a motor vehicle. It should also be noted that in this basicconstruction of the system, there are corresponding numbers of pumps 32,valves 42 and motors 50. Finally, it may be noted that the motors 50 maybe of the same construction as the pumps 32 to minimize inventoryrequirements and provide an economical construction and operation.

The system 10 is particularly useful when the spacing between the wheels52 on opposite sides of the vehicle are substantially equal to theiength of the wheel base, that is, the spacing between a center linethrough the front wheels 52 (say those associated with motors M and Mand a center line through the rear wheels 52.

The ports 46 of all the valves 42 are connected in parallel to a commoncontrol valve 54, and the output of the valve 54 is in turn connected tothe sump. The valve 54 is designated V in the drawing to indicate itsfunction as a brake for the motors 50 as will be referred to more indetail below. The valve 54 may be of any suitable construction which mayprovide a throttling action.

OPERATION OF EMBODIMENT OF FIGS. lAND 2 In operation of the system 10,the engine 12 will be operated at a constant speed at all times it isdesired to either drive the vehicle containing the system 10, or tooperate auxiliary hydraulic equipment, such as a seismic vibrator, whichmay be mounted on the vehicle. The primary pump 14 is therefor alsooperated at a constant speed and directs a flow of fluid at a relativelyconstant pressure and variable volume to the inlet port 20 of the firstcontrol valve 22. When the auxiliary equipment is being operated, thecontrol valve 22 is shifted to a position such that the fluid dischargefrom the pump 14 is directed out the port 26, and the port 28 is closed.On the other hand, when it is desired to move the vehicle, the controlvalve 22 is operated to direct the discharge from the primary pump 14out the port 28 and the port 26 is closed. When the auxiliary equipmentis not being operated and the vehicle is not desired to be moved, thecontrol valve 22 can be positioned to direct the discharge from theprimary pump 14 out through the port 24 back to the sump, in the eventit is desired to keep the engine 12 and pump 14 in operation. However;the primary pump 14 may be so constructed as to have no output (have azero stroke) when the output pressure of the pump reaches apredetermined maximum value. In this latter event, the throttle valve 36may be closed and control valve 22 may be retained in a position to keepthe ports 20 and 28 thereof in communication when the vehicle isstationary and the auxiliary equipment is not being operated.

Let it be assume that it is desired to move the vehicle forward from astopped position. The control valve 22 will therefore be set in aposition to direct the discharge from the primary pump 14 to thethrottle valve 36. The throttle valve 36 is gradually opened to providea gradually increasing flow of fluid to the constant volume pumps 32 togradually accelerate the rotors of the pumps and the common shaft 34. Inview of the fact that the pressure at the inlet ports 30 of all of theconstant volume pumps 32 will be essentially the same, and in view ofthe fact that all of the rotors of the pumps are connected by the commonshaft 34, the pumps 32 will be operated at the same speed. It should befurther noted that the operating lever 51 of each of the control valves42 is turned to its forward or F position shown in FIG. 2. As a result,the fluid being discharged from each constant volume pump 32 will bedirected through its respective valve 42 and out through the respectiveport 44 to the forward port A of its respective motor 50. Thus themotors 50 will be gradually accelerated to drive the wheels 52 and movethe vehicle forward in a smoothly accelerating manner. The fluid beingdischarged from each motor 50 through its respective port B will bedirected into the port 48 of the respective valve 42 and out through therespective port 46 to the braking valve 54. Assuming the braking valve54 is in a fully opened position, this fluid will be simply returned tothe sump for reuse by the drive system 10.

Now assume it is desired to stop the vehicle and then reverse thedirection of the vehicle. The levers 51 are gradually moved from theirfull line F positions illustrated in FIG. 2 into the N or neutralpositions, at which time the fluid being discharged from each constantvolume pump 32 will be directed through the port 46 of the respectivevalve 42 and through the braking valve 54 to the sump, such that all ofthe motors 50 will simply be recirculating fluid through the valves 42.As previously noted, when a valve 42 is set to provide communicationbetween the ports 40 and 46 thereof, communication is also establishedbetween the ports 44 and 48 thereof. Thus the vehicle will coast to astop. It may also be noted that as the operating levers 51 are movedfrom the F to the N positions, the supply of fluid to the forward portsA of the motors 50 will be gradually reduced to prevent a sudden changein the operation of the motors.

To then reverse the direction of movement of the vehicle the operatinglevers 51 of all of the valves 42 are gradually moved from the Npositions to the R positions. During this movement of the operatinglevers, fluid from each constant volume pump 32 is directed into itsrespective port 48 at a gradually increasing rate to graduallyaccelerate the motors 50 in the reverse direction. When the operatinglevers 51 reach the R positions, the vehicle will be moving in a reversedirection at a maximum speed, with the fluid flowing through each motor50 being discharged from the A port thereof and through the ports 44 and46 of its respective valve 42 to the braking valve 54.

When the throttle valve 36 is fully open, the vehicle associated withthe system will be driven at full speed, either forward or reverse,depending upon the settings of the operating levers 51. In either event,the motors 50 will all be operated at uniform speeds, even though one ofthe wheels 52 may lose traction. In the event one of the wheels 52 doeslose traction, the fluid flowing through the respective motor 50 willhave a minimum resistence to flow through the motor and the resultingreduced pressure on the forward port A or reverse B thereof (dependingupon whether the vehicle is moving forward or reverse) is reflected backto the discharge port 38 of the respective associated constant volumepump 32. The increased pressure differential across that pump willconvert that pump into a motor to apply torque on the common shaft 34and thereby increase the pressure output of each of the remainingconstant volume pumps. As a result, the power not being utilized inoperating a wheel which has lost traction will be automaticallytransferred to the other Wheel of the vehicle which is being driven bythe system 10, to assure that adequate power will be available formoving the vehicle. Conversely, should one of the wheels 52 tend tobecome stuck and the rotation thereof retarded, an increased pressuredifferential will build up between the ports A and B thereof andincrease the back pressure on the associated constant volume pump 32,tending to retard the speed of rotation of all the constant volume pumps32. However, the power being supplied by the remaining constant volumepumps 32 on the common shaft 34 will tend to continue rotation of theaffected constant volume pump 32, such that an additional force ortorque will be exerted on the rotor of the affected constant volume pumpto overcome the back pressure resulting from the affected Wheel 52.

When the vehicle employing the drive system 10 is in full forward orfull reverse, the vehicle may be quickly stopped by closing the brakingvalve 54. To this end, the braking valve 54 is preferably treadleoperated by the driver of the vehicle. As the valve 54 is closing, theflow from each of the. motors 50 is progressively decreased to retardthe speed of rotation of the motors 50. And, when the valve 54 is fullyclosed, fluid will be prevented from flowing through any of the motors50; and the motors 50, along with their associated wheels 52, will beheld in a stopped position. The throttle valve 36 is preferably closedat the same time as the braking valve '54 to minimize back pressure onthe constant volume pumps 32. It should be noted that the back pressureon all of the motors 50 imposed by closing the braking valve 54 willprevent the motors from cavitating, as would be the case if the vehiclewere stopped by closing the throttle valve 36 while applying amechanical bra-king action on the wheels 52 and the wheels were notstopped before the supply of fluid was stopped.

Let it now be assumed that the vehicle is being moved full forward andthe wheels associated with the motors M and M are the front wheels ofthe vehicle. Let it be further assumed that the vehicle is to be turnedto the right. In this event, the operating lever 51 associated with thevalve 42 connected to the motor M will be moved from the F toward the -Nposition to bypass a portion of the fluid from the respective constantvolume pump 32 to the sump via the port 46 of the respective valve toretard the speed of rotation of the respective wheel 52. At the sametime, the lever 51 associated with the valve 42 connected to the motor Mwill also be moved toward a neutral position, but to a lesser extent, toretard the speed of rotation of the associated motor 50 and accommodatethe turning of the vehicle. The speed of operation of the motor M may bevaried in a like manner and to an extent depending upon the shortness ofthe turn being made by the vehicle. When turning to the left, motors Mand M and perhaps motor M would be slowed in a similar manner. Thevehicle may also be turned by placing the operating levers 51 of thevalves 42 associated with the wheels on one side of the vehicle in theirneutral positions while retaining the levers 51 of the valves associatedwith the wheels on the opposite side of the vehicle in their F or Rpositions. Since the motors 50 associated with the valves 42 havingtheir ope-rating levers 51 in neutral position will simply free wheel,the vehicle will turn gradually toward that side.

EMBODIMENT OF FIG. 3

A vehicle employing the present drive system may also be steered bydriving the wheels on one side of the vehicle at one speed and drivingthe wheels on the other side of the vehicle at a different speed,similar to the method of steering tractors and other large vehicleshaving a single track on each side thereof. To utilize such a steeringmethod, the valves 42 controlling the operation of the motors M and Mhave their operating levers 51 connected to a common linkage 56 asschematically illustrated in FIG. 3. Operating levers 51 of the valves42 controlling the motors M and M are similarly connected by a linkage58. With this arrangement it will be seen that the motors M and M, willbe operated at the same speeds and in the same direction by manipulationof a linkage S6, and the motors M and M will be operated at the samespeeds and in the same direction by manipulation of the linkage 58.Thus, the motors M and M may be decreased in speed, or stopped, whilethe motors M and M are operated at a higher speed to turn the vehicle tothe left. The reverse operation of the motors would cause the vehicle toturn to the right.

In some environments it is desirable to utilize tracks rather thanwheels for supporting the vehicle. Under these circumstances, the wheels52 on one side of the vehicle may receive a single, continuous tracktherearound, while the wheels 52 on the opposite side of the vehiclereceive a similar track. It would then be necessary to drive only asingle motor on each side of the vehicle. With this arrangement, theports 48 of the valves 42 associated with the Wheels and motors on oneside of the vehicle may be interconnected by a conduit 60 and 3-wayvalve 61, and the ports 44 of the same two valves 42 may beinterconnected by a conduit 62 and 3-Way valve 64. The same arrangementwould apply for the remaining two valves 42 associated with the wheelsand motors on the opposite side of the vehicle.

With a system as illustrated in FIG. 3 and as just described, all of thefluid discharged from the two constant volume pumps 32 associated withthe motors M and M may, by proper positioning of the associated valves61 and 64, be directed either to the forward port A of the motor M or tothe reverse port B of the motor M to provide a maximum application ofpressure to such motor. Similarly, all of the fluid discharged from thetwo constant volume pumps 32 associated with the motors M and M may, byproper positioning of the associated valves 61 and 64, be directedeither to the forward port A of the motor M or to the reverse port B ofthe motor M It will also be understood either the motor M or the motor Mcould be placed in either a free wheeling condition for a gradual turnor a reverse condition for a sharp turn of the vehicle to the left orthe right, as the case may be. On the other hand, if the tracksextending around the wheels on each side of the vehicle were laterremoved for use of the vehicle in a different environment, the valves 61and 64 may be positioned to close off the conduits 60 and 62. In thislatter event, both motors on each side of the vehicle would be su-ppliedwith equal amounts of fluid in the same manner as previously describedin connection with FIG. 1.

EMBODIMENT OF FIG. 4

In the event the motors 50 do not utilize equal amounts of fluid forequal speeds of operation, such as when a motor becomes worn and morefluid must be passed through the motor to obtain a speed of operationequal to the speed of operation of a new motor, the modification shownin FIG. 4 may be utilized. In this modification, a valve 66 may beconnected across the ports A and B of each motor 50 to bypass a selectedamount of fluid around one or more of the motors. For example, if one ofthe motors 50 is worn more than another motor 50, a portion of the fluiddelivered to the unworn motor could be bypassed by means of theassociated valve 66 to equalize the speeds of operation of the motorswhen the motors were being supplied with equal amounts of fluid fromtheir associated constant volume pumps 32. The valves 66 will berequired to bypass a very moderate amount of fluid and will thereforenormally be needle type valves, or equivalent.

EMBODIMENT OF FIG. 5

For shipboard use, it is preferable to employ a plurality of primemovers 12, such as three diesel engines as shown in FIG. 5, as a safetymeasure. With this arrangement, each engine 12 is drivingly connected toa primary pump 14, and each primary pump 14 is in turn connected to acontrol valve 22 in the same manner as previously described. One port ofeach control valve 22 may be connected to hydraulically driven auxiliaryequipment and the ports 28 of all of the control valves 22 are connectedin parallel to a pair of constant volume pumps 32. The rotors of theconstant volume pumps 32 are mounted on a common shaft 34, as before,and the output of each constant volume pump 32 is directed to ahydraulic motor 50 through a four-way, open-center valve 42 in the samemanner as in the system previously described in connection with FIG. 1.Each hydraulic motor 50 is drivingly connected to a propeller 68employed in propelling the ship. With this arrangement, two propellers68 are normally required and the motors 50 may be mounted on the outsideof the hull of the ship to prevent the necessity of extending the driveshafts of the propellers through the hull. Auxiliary propellers givingside thrust at the bow or stern, or both, may also be utilized in thesystem and such auxiliary propellers may be driven by motors connectedto the control valves 22 if desired.

In operation of the shipboard version of the present drive system asshown in FIG. 5, either two or all three of the engines 12 are operatedat the same time, particularly when the auxiliary equipment is beingoperated at the same time the ship is underway. With this arrangement,one or two of the control valves 22 may be turned to direct the outputof the associated pump 14 to the auxiliary equipment, while theremaining control valve or valves 22 is turned to direct the output ofthe associated pump 14 to the inlets of the constant volume pumps 32.The constant volume pumps 32, valves 42 and motors 5t) operate in thesame manner as previously described in connection with FIG. 1 to drivethe propellers 68 at the desired speeds and in the desired directionswith the exception that, in this system, the valves 42 are preferablyemployed as the sole means for accelerating and decelerating thepropellers 68.

In the event the auxiliary equiment is not required to be in operationwhile the ship is underway, all of the control valves 22 may be turnedto direct the outputs of the pumps 14 to the constant volume pumps 32.Further, in the event of a malfunction of one or two of the .engines 12,the remaining engine or engines may be employed to operate the constantvolume pumps 32 at a reduced power with full steering andmaneuverability of two (or more) propellers available from only oneoperating engine until the malfunction can be controlled.

From the foregoing it will be apparent that the present inventionprovides a hydraulic drive system for a plurality of hydraulic motorswherein the system is highly adaptable and may be employed in variousenvironments. When used on a vehicle containing hydraulically operatedauxiliary equipment, such as seismic vibrators, the same prime mover isemployed for operating the auxiliary equipment and the drive system andthe power supplied by the prime mover may be quickly and easily directedto either the auxiliary equipment or the drive system for moving thevehicle. When the present drive system is employed on vehicles, thevehicles can be used on a great variety of terrains, using four wheeldrives, two wheel 9 drives, or track drives. When used aboard ship, thepresen drive system is highly adaptable and will reduce both the firstand maintenance costs of the ship.

Changes may be made in the arrangement and combination of parts orelements as herefore set forth in the specification and shown in thedrawing without departing from the spirit and scope of the invention.

What is claimed is:

1. A system for driving a plurality of hydraulic motors, each of whichhas a forward and a reverse port, comprising:

a prime mover;

a primary pump drivingly connected to the prime mover and having aninlet and an outlet;

a supply of hydraulic fluid connected to the inlet of the primary pump;

a rotary, constant volume pump for each of the hydraulic motors to bedriven and being capable of functioning as a motor as well as a pump,each of said constant volume pumps having an inlet and an outlet withthe inlet thereof connected to the outlet of the primary pump;

a common shaft connected to the rotors of all of said constant volumepumps for transfering power between said constant volume pumps; and

a four-way, open-center valve for each constant volume pump having afirst port connected to the outlet of the associated constant volumepump, a second port connected to the forward port of the associatedmotor, a third port connected to the reverse port of the associatedmotor, and a fourth port connected to the fluid supply;

each of said valves having an operating lever adapted to be positionedto direct (a) all of the fluid discharged from the associated constantvolume pump to either port of the associated motor; (b) a variableportion of the fluid discharged from the associated constant volume pumpto either port of the associated motor while directing the remainingportion of said discharge to the fluid supply; and alternately, (c) allof the fluid discharged from the associated constant volume pump to thefluid supply while providing communication between the second and thirdports of the respective valve, whereby both the speed and direction ofrotation of each motor may be individually controlled,

2. A system as defined in claim 1 characterized further to include acontrol valve having an inlet and an outlet;

means connecting the outlet of the control valve to the fluid supply;and

means connecting the inlet of the control valve to the fourth ports ofall of the four-way, open-center valves,

whereby a back pressure may be selectively imposed on the outlets of themotors and form a braking action on the motors while preventingcavitation in the motors.

3. A system as defined in claim 1 characterized further to include athrottle valve interposed in the connection of the primary pump to theconstant volume pumps, whereby the speeds of the motors may becontrolled as a group.

4. A system as defined in claim 1 characterized further to include abypass control valve interconnecting the forward and reverse ports ofeach motor to selectively bypass fluid around any of the motors in theevent all of the motors do not require the same amount of fluid for thesame speed of operation.

5. A system as defined in claim 1 characterized further to include asecond prime mover, a second primary pump drivingly connected to thesecond prime mover having an inlet connected to the fluid supply and itsoutlet connected to the inlets of all the constant volume pumps.

6. A drive system for a vehicle having a pair of wheels 10 on each sidethereof with the wheels on each side adapted to selectively receive acrawler track extending around both wheels, comprising:

a prime mover;

a primary pump drivingly connected to the prime mover, and having aninlet and an outlet;

a supply of hydraulic fluid connected to the inlet of the primary pump;

a rotary, constant volume pump for each of the wheels capable offunctioning as a motor as well as a pump, each of said constant volumepumps having an inlet and an outlet with the inlet thereof connected tothe outlet of the primary pump;

a common shaft connected to the rotors of said constant volume pumps fortransferring power between said constant volume pumps;

a rotary, fluid motor drivingly connected to each of the wheels of thevehicle, each of said motors having a forward and a reverse port;

a four-way, open-center valve for each constant volume pump andassociated motor having a first port connected to the outlet of theassociated constant volume pump, a second port connected to the forwardport of the associated motor, a third port connected to the reverse portof the associated motor, and a fourth port connected to the fluidsupply;

an operating lever on each of said valves adapted to be positioned todirect (a) all of the fluid discharged from the associated constantvolume pump to either port of the associated motor; (b) a variableportion of the fluid discharged from the associated constant volume pumpto either port of the associated motor while directing the remainingportion of said discharge to the fluid supply; and, alternately, (c) allof the fluid discharged from the associated constant volume pump to thefluid supply while providing communication between the second and thirdports of the respective valve;

a conduit and 3-way valve interconnecting the second ports of the valvesassociated with the motors on each side of the vehicle for selectivelydirecting the fluid discharged from the associated constant volume pumpsto the forward port of only one of the associated motors; and

a conduit and 3-way valve interconnecting the third ports of the valvesassociated with the motors on each side of the vehicle for selectivelydirecting the fluid discharged from the associated constant volume pumpsto the reverse port of only one of the associated motors.

7. A drive system for a vehicle having a pair of wheels on each sidecomprising:

a prime mover;

a primary pump drivingly connected to the prime mover, and having aninlet and an outlet;

a supply of hydraulic fluid connected to the inlet of the primary pump;

a rotary, constant volume pump for each of the wheels capable offunctioning as a motor as well as a pump, each of said constant volumepumps having an inlet and an outlet with the inlet thereof connected tothe outlet of the primary pump;

a common shaft connected to the rotors of said constant volume pumps fortransferring power between said constant volume pumps;

a rotary, fluid motor drivingly connected to each of the wheels of thevehicle, each of said motors having a forward and a reverse port;

a four-way, open-center valve for each constant volume pump andassociated motor having a first port connected to the. outlet of theassociated constant volume pump, a second port connected to the forwardport of the associated motor, a third port connected to the reverse portof the associated motor, and a fourth port connected to the fluidsupply;

an operating lever on each of said valves adapted to be means providingsubstantially equal volumes of fluid positioned to direct (a) all of thefluid discharged for the motors; from the associated constant volumepump to either a supply of hydraulic fluid connected to said means; andport of the associated motor; (b) a variable portion a four-way,open-center valve for each motor having of the fluid discharged from theassociated constant a first port connected to one of said means, asecond volume pump to either port of the associated motor port connectedto the forward port of the associated while directing the remainingportion of said dismotor, a third port connected to the reverse port ofcharge to the fluid supply; and, alternately, (c) all the associatedmotor, and a fourth port connected of the fluid discharged from theassociated constant to th fluid supply; volume pump to the fluid supplywhile providing each of said valves having an operating lever adaptedcommunication between the second and third ports to be positioned todirect (a) all of the fluid disot' the respective valve; charged fromthe respective means to either port of a first linkage connected to theoperating levers of the the associated motor; (b) a variable portion ofthe four-way valves associated with the. motors on one fluid dischargedfrom the respective means to either side of the vehicle forcorresponding movements of 15 port of th a o iated motor whil directingthe resaid levers; and maining portion of said discharge to the fluidsupply; a second linkage connected to t Operating levers Di andalternately, (c) all of the fluid discharged from the four-way valvesassociated With the motors On the respective means to the fluid supplywhile providthe opposite side of the vehicle fOI. corresponding ingcommunication between the second and third movements of said levers.ports of the respective valve, whereby both the speed '8. A system fordriving a plurality of propellers and auxiliary equipment of a ship,comprising:

a plurality of prime movers; a. primary pump for each prime moverdrivingly connected to the respective prime mover and having ancomprising; inlet and an outlet; means providing substantially equalvolumes of fluid for a supply of hydraulic fluid connected to the inletsof th m t the primary pumps; a supply of hydraulic fluid connected tosaid means; a P r of rot ry, Constant Volume P p Capable of a four-way,open-center valve for each motor having functioning as motors as Well asP p each of Said a first port connected to one of said means, a secondand direction of rotation of each motor may be individually controlled.10. A system for driving a plurality of hydraulic moconstant volumepumps having an inlet and an outlet tors, each of which has a forwardand a reverse port,

with the inlet thereof connected to the outlets of all the primarypumps; common shaft connected to the rotors of said conport connected tothe forward port of the associated motor, a third port connected to thereverse port of the associated motor, and a fourth port connected to thefluid supply;

stant volume pumps for transferring power between said constant volumepumps;

a four-way valve interposed in the connection of each primary pump andthe constant volume pumps having a third port connected to the auxiliaryequipment and a fourth port connected to the fluid supply; 4

a rotary, fluid motor for each propeller drivingly connected to therespective propeller;

a four-way, open-center valve for each constant volume pump andassociated motor having a first port connected to the outlet of theassociated constant volume pump, a second port connected to the forwardport of the associated motor, a third port connected to the reverse portof the associated motor, and a fourth port connected to the fluidsupply; 7

an operating lever on each of said four-Way, open-center valves adaptedto be positioned to direct (a) all of the fluid discharged from theassociated constant volume pump to either port of the associated motor;'(b) a variable portion of the fluid discharged from the associatedconstant volume pump to either port of the associated motor Whiledirecting the remaining each of said valves having an operating leveradapted to be positioned to direct (a) all of the fluid discharged fromthe respective means to either port of the associated motor; (b) avariable portion of the fluid discharged from the respective means toeither port of the associated motor while directing the remainingportion of said discharge to the fluid supply; and alternately (c) allof the fluid discharged from the respective means to the fluid supplywhile providing communication between the second and third ports of therespective valve, whereby both the speed and direction of rotation ofeach motor may be individually controlled; and

a valve interposed in the connection between all of the fourth ports ofthe four-way, open-center valves and the fluid supply adapted torestrict the discharge of fluid from the motors and the four-way,open-center valves to provide a braking action on the motors.

References Cited UNITED STATES PATENTS portion of said discharge to thefluid supply; and, 2,291,578 7/ 1942 1011118011- alternately, (c) all ofthe fluid discharged from the 2,301,098 11/ 1942 TWymaI! -53 XRassociated constant volume pump to the fluid supply 2,316,926 9 3WiHett.

While providing communication between the e 60 2,431,719 12/1947 Wilkin60 53 0nd and third ports of the respective four-way, open- ,437,139 3/1948 Tucker 6 0-53 XR center valve, whereby both the speed and directionof rotation of the propellers may be individually controlled. 9. Asystem for driving a plurality of hydraulic motors, each of which has aforward and a reverse port, comprismg:

EDGAR W. GEOGHEGAN, Primary Examiner

